Core Polarization and Tensor Coupling Effects on Magnetic Moments of Hypernuclei

The effects of core polarization and tensor coupling on the magnetic moments in $^{13}_\Lambda$C, $^{17}_\Lambda$O, and $^{41}_\Lambda$Ca $\Lambda$-hypernuclei are studied in the Dirac equation with scalar, vector and tensor potentials. It is found that the effect of core polarization on the magnetic moments is suppressed by $\Lambda$ tensor coupling. The $\Lambda$ tensor potential reduces the spin-orbit splitting of $p_\Lambda$ states considerably. However, almost the same magnetic moments are obtained using the hyperon wave function obtained via the Dirac equation either with or without the $\Lambda$ tensor potential in the electromagnetic current vertex. The deviations of magnetic moments for $p_\Lambda$ states from the Schmidt values are found to increase with nuclear mass number.Comment: 10 pages, 2 figures, 2 table

A systematic study on the binding energy of Λ\Lambda hypernuclei

In this paper, we calculated the binding energy per baryon of the $\Lambda$ hypernuclei systemically, using the relativistic mean field theory (RMF) in a statistic frame. Some resemble properties are found among most of the hypernuclei found in experiments. The data show that a $\Lambda$ hypernucleus will be more stable, if it is composed of a $\Lambda$ hyperon adding to a stable normal nuclear core, or a $\Lambda$ hyperon replacing a neutron in a stable normal nuclear core. According to our calculations, existences of some new $\Lambda$ hypernuclei are predicted under the frame of RMF.Comment: 8 pages, 6 figures, 3 table

Impurity effect of Λ\Lambda hyperon on shape-coexistence nucleus 44^{44}S in the energy functional based collective Hamiltonian

The non-relativistic Skyrme energy density functional (EDF) based collective Hamiltonian, that takes into account dynamical correlations related to the restoration of broken symmetries and fluctuations of quadrupole collective variables, is applied to quantitatively study the impurity effect of $\Lambda$ hyperon on the collectivity of $^{44}$S. Several Skyrme forces for both the nucleon-nucleon ($NN$) and $\Lambda$-nucleon ($\Lambda N$) interactions are used. The influence of pairing strengths on the polarization effect of $\Lambda$ hyperon is also examined. It is found that although these Skyrme forces with different pairing strengths give somewhat different low-lying spectra for $^{44}$S, all of them give similar and generally small size of $\Lambda$ reduction effect (within 5%) on the collective properties.Comment: 8 pages, 5 figures, based on the talk presented at 18th Nuclear Physics Workshop "Maria and Pierre Curie", 2011, Kazimierz, Polan

Antimatter production in proton-proton and heavy-ion collisions at ultrarelativistic energies

One of the striking features of particle production at high beam energies is the near equal abundance of matter and antimatter in the central rapidity region. In this paper we study how this symmetry is reached as the beam energy is increased. In particular, we quantify explicitly the energy dependence of the approach to matter/antimatter symmetry in proton-proton and in heavy-ion collisions. Expectations are presented also for the production of more complex forms of antimatter like antihypernuclei.Comment: 7 pages, 5 figure

Phenomenological study of light (anti)nuclei, (anti)hypertriton and di-Lambda production at RHIC

We present the production of light (anti)nuclei, (anti)hypertriton and di-Lambda based on coalescence model in central Au+Au collisions at $\sqrt{s_{NN}}=200GeV$. The invariant yields of \He(\Hebar), \hypert(\hypertbar), \Hee(\Heebar) obtained is found to be consistent with the STAR measurements. The $p_{T}$ integrated yields for di-Lambda $dN_{\Lambda\Lambda}/dy \sim 2.23\times10^{-5}$, and is not strongly dependent on the parameter employed for coalescence process. Relative particle ratios of light anti(nuclei) and (anti)hypertriton are explored, and agree with experimental data and thermal model predictions quite well. An exponential reducion behavior is presented for the differential invariant yields with increased baryon number. The production rate reduces by a factor of 1692 (1285) for each additional antinucleon (nucleon) added to antinuclei (nuclei), and the production rate of \Libar is predicted to be $10^{-16}$ which is consistent with STAR result.Comment: 4 pages, 3 figures parallel talk delivered by L. Xue at the 14th national conference on nuclear structure, April 12nd - 16th, 2012, Huzhou, Chin

The Lambda-Lambda Interaction and ^{6}_{Lambda Lambda}He

An OBE potential model for the ^{1}S_0 S = -2 interaction is analyzed with emphasis on the role of coupling between the Lambda Lambda, N Xi, and Sigma Sigma channels. Singlet scalar exchange, an approximation to two-pion exchange, is significant in all channels; surprisingly, the one-pion exchange component is almost negligible. The size of the channel coupling as a function of the overall strength of the OBE model potential is examined. Implications of the analysis for the binding energy of ^{6}_{Lambda Lambda}He are considered; the new experimental datum may suggest a consistency between the extracted Lambda Lambda matrix element and the relation implied by SU(3) among OBE baryon-baryon interactions. \\Comment: 4 pages brief report to Physical Review

Nuclei, Superheavy Nuclei and Hypermatter in a chiral SU(3)-Modell

A model based on chiral SU(3)-symmetry in nonlinear realisation is used for the investigation of nuclei, superheavy nuclei, hypernuclei and multistrange nuclear objects (so called MEMOs). The model works very well in the case of nuclei and hypernuclei with one Lambda-particle and rules out MEMOs. Basic observables which are known for nuclei and hypernuclei are reproduced satisfactorily. The model predicts Z=120 and N=172, 184 and 198 as the next shell closures in the region of superheavy nuclei. The calculations have been performed in self-consistent relativistic mean field approximation assuming spherical symmetry. The parameters were adapted to known nuclei.Comment: 19 pages, 11 figure

Strange Exotic States and Compact Stars

We discuss the possible appearance of strange exotic multi-quark states in the interior of neutron stars and signals for the existence of strange quark matter in the core of compact stars. We show how the in-medium properties of possible pentaquark states are constrained by pulsar mass measurements. The possibility of generating the observed large pulsar kick velocities by asymmetric emission of neutrinos from strange quark matter in magnetic fields is outlined.Comment: 10 pages, invited talk given at the International Conference on Strangeness in Quark Matter 2006 (SQM2006), UCLA, USA, March 26-31, 2006, Journal of Physics G in press, refs. adde

Quadrupole deformation (β,γ)(\beta,\gamma) of light Λ\Lambda hypernuclei in constrained relativistic mean field model: shape evolution and shape polarization effect of Λ\Lambda hyperon

The shapes of light normal nuclei and $\Lambda$ hypernuclei are investigated in the $(\beta, \gamma)$ deformation plane by using a newly developed constrained relativistic mean field (RMF) model. As examples, the results of some C, Mg, and Si nuclei are presented and discussed in details. We found that for normal nuclei the present RMF calculations and previous Skyrme-Hartree-Fock models predict similar trends of the shape evolution with the neutron number increasing. But some quantitative aspects from these two approaches, such as the depth of the minimum and the softness in the $\gamma$ direction, differ a lot for several nuclei. For $\Lambda$ hypernuclei, in most cases, the addition of a $\Lambda$ hyperon alters slightly the location of the ground state minimum towards the direction of smaller $\beta$ and softer $\gamma$ in the potential energy surface $E \sim (\beta, \gamma)$. There are three exceptions, namely, $^{13}_\Lambda$C, $^{23}_\Lambda$C, and $^{31}_\Lambda$Si in which the polarization effect of the additional $\Lambda$ is so strong that the shapes of these three hypernuclei are drastically different from their corresponding core nuclei.Comment: 11 pages, 3 figures; added references and arguments in Sections III and IV; to be published in Phys. Rev.

Θ+\Theta^{+} hypernuclei in relativistic mean field model

We have investigated the properties of $\Theta^{+}$ in nuclei within the framework of relativistic mean field. The coupling constants are educed with quark meson coupling model. There is strong attractive interaction for $\Theta^{+}$-nucleus and $\Theta^{+}$ can be bind in nuclei. The depth of optical potential for $\Theta^{+}$ in nuclear matter is estimated.Comment: 12 page